Buildings such as factories are often ventilated to ensure air circulation. Factories where foods are prepared will typically operate at a positive pressure compared to ambient. Air is drawn in from the outside by fans and is blown into the factory via ducting. Operating at a positive air pressure will ensure that external contaminants are not drawn into the factory via door and other openings. Airflow will be in an outward direction through such openings.
Air being blown in by the fans will itself carry contaminants such as pollen, bugs and other items undesirable inside the factory. These need to be filtered. Current air filtration systems rely on multistage filtration. Ambient air will pass through several banks of filters before entering the factory proper. Air will first encounter course filters and gradually be blown (or sucked) through finer filters. Each filter taking away more contaminants in the airflow so that sufficiently clean air makes its way into the factory.
The patent specification of U.S. Pat. No. 4,197,099 shows a typical filter arrangement that may be used where a frame is provided against which a filter bag is able to be clipped. The filter bag has a perimeter frame itself that provides for perimeter contact to be established between the filter bag and the frame with a view to sealing between. The frame and the filter bag are ideally sealed to each other by the use of a compression force and appropriate interface material selection. Clips, as shown in U.S. Pat. No. '099, may be used to help this. Clips are used in order to allow for a quick filter change to occur from time to time. Filters may be removed and replaced once they become sufficiently clogged up. Some filters are able to be cleaned and reused. Having a quick fit mechanism for removing and replacing filters is an advantage.
But contaminants can still find a way past the filters because only slight or no pressure exists between the filter frame and the main frame midway between the corners and where the clips are acting. Contaminants such as bugs like flies and other small insects are known to be able to make their way past the interface of the frame and the filter.
There is hence a need for an improved filtration system and related component that provide a better barrier to contaminants and/or that will at least provide the public with a useful choice.